DESCRIPTION: This is a new application from Boston University that addresses the role of adjuvant tamoxifen therapy in older women with breast cancer. Although there has been interest in variations in the use of mastectomy vs. breast-conserving surgery + radiation therapy among older women, there has been little systematic study of the use of adjuvant therapy outside of clinical trials. The use of chemotherapy in older postmenopausal women remains controversial, however, adjuvant tamoxifen has been proven to be efficacious in reducing recurrences and mortality in older women, with no apparent decrement in efficacy by age, including those women 70 years of age and older. In spite of published guidelines recommending the use of tamoxifen in postmenopausal women with tumors > 1 cm, there is evidence that older women are being under-treated and that the rates of tamoxifen discontinuance are not inconsequential. This application proposes a prospective observational study of women > 70 years of age with stage I (> 1 cm) and stage II breast cancer and of their physicians in diverse health care settings in four different geographic regions (Los Angeles, the states of Minnesota and Rhode Island, and Western North Carolina), with differing rates of tamoxifen use. The four primary aims of this research are to identify predictors of 1) physicians' beliefs regarding the benefits and risks of adjuvant tamoxifen therapy in older women; 2) patients' beliefs regarding the benefits and risks of adjuvant tamoxifen therapy and of changes in these beliefs over a one-year period of time; 3) physicians' prescribing of tamoxifen; and 4) patients' adherence to tamoxifen therapy at three and twelve months post tamoxifen prescription. The two secondary aims of the research are to compare tamoxifen-treated and untreated women with respect to: 1) the prevalence of symptoms commonly attributed to tamoxifen therapy and 2) health-related quality of life.